I have some info. I developed this same ileopsoas tendinitis two weeks after left hip and two weeks after right hip replacement. The surgeon denied it could be the hip causing this. He sent me to a rheumatologist and low back surgeon, wasting my money. He is considered the best surgeon in the state! He got so frustrated with me. The pain became so severe I could barely walk. I was in misery. Finally, he put cortisone in the trochanter bursa and the pain went away in a couple days. When the same pain occurred after the second hip, I got the cortisone. I have also tried cortisone directly into, by ultrasound, the tendon. That did not work any better than just doing the bursa. So every three months for five times each hip, I got cortisone. I went to PT and stretching made the pain severe and debilitating. I also had several dry needling from the PT which did nothing.
In addition, recent cadaver studies have confirmed the presence of a sixth muscle, the tensor vastus intermedius.  While the muscle has variable presentations, it consistently originates at the proximal femur, runs between the vastus lateralis and vastus intermedius muscles, and inserts distally at the medial aspect of the patellar base.  Historically considered a part of the vastus lateralis , the tensor vastus intermedius muscle is innervated by an independent branch of the femoral nerve and its tendinous belly can be separated from the vasti lateralis and intermedius muscles in most cases. 
This posture can also distort the lower back (lumbar spine) from it’s normal curve. It is meant to stack up in a curve, and not curve backward. With that reverse curve position, the front edges of the vertebrae press together and can squeeze disc material out toward the back of the spine where the nerves are located. If the pressure on the nerves is sufficient or the discs are leaking fluids containing irritating chemicals, it can hurt. The position also affects the muscles, compressing some and stretching others. Constant poor positioning can cause the muscles to contract and even go into spasm.